A standard stair climber for a wheelchair, stretcher, or the like has a support adapted to engage underneath the wheelchair in an upright condition of same with the wheelchair pivotal on the support between erect and inclined positions. The wheelchair is moved onto this support at the top or bottom of the incline or flight of stairs. Two endless tracks carry the support and wheelchair thereon so the wheelchair can move over uneven terrain and up and down stairs.
In order to move on an incline it is necessary to tip the wheelchair back into the inclined position, as otherwise the assembly would overbalance forward, presuming that the chair is facing down the incline. A latch on the support is displaceable between a holding position securing the wheelchair in the inclined position and a freeing position permitting the wheelchair to move freely between its positions. This latch is typically operated by a foot lever or pedal.
Although the latch is made as robust as impossible, it is not impossible for the pedal to be depressed accidentally. This can happen when an attendant who is rolling the chair on the level is following too closely or guiding the stair-climbing apparatus. Such actuation can open the latch, allowing the wheelchair to tip forward and dump out the disabled person in it, with the obvious risks.